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Questions tagged [digital-communications]

Related to all communication systems that use a given digital sequence as an interface between the source and the channel input.

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39 views

which device to use to convert analog signal to full fledged digital signal? [on hold]

Am thinking of project of digital transmission of music over laser. But the thing which isn't clear to me is, I know theory behind all this stuff like analog signal then sampling, quantization, Delta ...
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1answer
28 views

Source generator for Satellite Tuner input

I need to design a source generator for a TV factory. They want to automatize the functional tests by applying a test module to the TV's at the end of the production line. All the peripherals of the ...
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1answer
39 views

What is the effect of redundancy coding on the bit error rate?

If I have a channel with bit error rate BER = \$10^{-3}\$ after modulation, but this is too high so I decide to add repetition coding. With 2 code words and block length of 3 such that I have a ...
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3answers
81 views

Choosing best bus and protocol for ~128 clients over the wire

I am up to design system with ~128 MCUs communicating to one MCU master. Communication will be bidirectional. Data will be mostly sensor reads, but I plan to use the bus also as communication method ...
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1answer
82 views

How do I stop signal looping with I/O port in this communication system

I am still a student. When I am designing communication system I am facing this problem: As shown in the figure I need to communicate with Master and Slave. But Master and Slave have single I/O port ...
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3answers
68 views

How is companding different from pre-emphasis and de-emphasis?

What I know is that interference increases linearly with frequency and thus noise power is concentrated at higher frequency. So, to reduce noise, pre-emphasis and de-emphasis filters are used which ...
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1answer
55 views

Signed and unsigned numbers in verilog

I understand the concept of fixed point and multiplying signed with unsigned by sign extension the unsigned number with 1 bit of '0' so it will be signed always positive number, But my question If I ...
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1answer
72 views

UART Transmit issue in VHDL

I'm working on a UART transmit process (uart_transmit) in VHDL (115200 baud, 8 data bits, 1 stop bit and no parity). I need the transmit line ...
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1answer
82 views

Are horizontal and vertical back porches required for digital video, and if so, why?

The necessity of vertical and horizontal front and back porches in analog video seem fairly intuitive to me, but why are they necessary for digital video at all? In this LCD module data sheet and this ...
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1answer
66 views

In wireless communication, what is “channel length”?

In wireless communication, I am confused about what people are referring to when they use the term 'channel length.' Can someone explain the term or provide me a definition?
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0answers
57 views

High data rate (~1-5 Mpbs) Point to Point Radio

I'm working on a rocket project at my University, and am trying to find a point to point / point to multipoint radio capable of a hopefully 1-5 Mbps data rate between a ground station a directional ...
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2answers
140 views

What device can convert (EEG) voltage data to real voltage? [closed]

I seek a device that can be programmed to output physical voltages based on a set of datapoints. For example: ...
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1answer
49 views

Inverse Z-transform Problem [closed]

I'm rather stuck trying to compute the inverse Z-transform y[n] of the function below. I'm having trouble selecting the correct formulas from the table to achieve the right solution. Any help with ...
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1answer
55 views

Ringing issue on I2C FM+ bus between MCU and few sensors - Power supply issue?

I'm experiencing some issues while probing a problematic I2C bus on the oscilloscope. We want to interface several TLV493D-A1B6, with a STM32L4 (we are working as well on STM32F4 and have the same ...
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3answers
48 views

Practical Limitations to 1-Wire Communication Speed [closed]

What are some practical limitations to the speed of a 1-Wire interface?
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2answers
141 views

Can someone explain the use of the transistor in this circuit?

I came across a schematic which implemented a 1 Wire interface. However, this 1-Wire interface circuit also includes a transistor connected as shown in the picture. Can somebody expain why this has ...
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5answers
79 views

RS485 IC Termination Resistor Configuration

I've made a mistake on a design, that went into production... It was built like the drawing on the left, with R702 to 5V and R703 to GND, it should have been backwards... like the drawing on the ...
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0answers
50 views

Derivation of stability criterion for type 3 digital PLL

Could anyone help to derive the following expression (4.23) which is the stability criterion for type 3 digital PLL ? Note: Screenshots are taken from Floyd Gardner's book : Phaselock Techniques 3rd ...
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1answer
31 views

What are cost-effective and ways of providing global communication between two devices besides internet and SMS?

I am currently in the process of building a system which allows vehicles to send information back and forth with an Arduino. The main problem I am facing right now, is that the current implementation ...
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2answers
53 views

Geometric representation of GMSK signal

Can anyone provide me the geometric representation of GMSK signal? Also, am I correct in saying that bit energy of GMSK is same as its symbol energy since MSK is a binary modulation scheme with only ...
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1answer
52 views

Printer Data Cables with *suspected* IC boards [duplicate]

I've one found of those printer data cables that have some kind of pair integrated circuit along them, one at each end just before the plugs, I was wondering if there is a less invasive way of ...
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1answer
75 views

Asynchronous FIFO in clock domain crossing

Clock domain crossing issue can be solved by using asynchronus FIFO with input frequency f1 is of the source domain and f2 is of the destination frequency. If the data is sent in bursts, depth can be ...
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2answers
142 views

Using optocouplers at the end of a twisted pair

I am designing a dumb "isolation box" that is to sit between a computer and medical data acquisition equipment. The purpose of this box is to inject power and to provide communications and digital ...
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1answer
53 views

How to know voltage used on a data bus?

How do you find out what voltage is being used on a data bus for the high signal? On a small electronics I guess you can assume it will be 3.3v or 5v but what about other circuits, say in a car or on ...
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1answer
31 views

How can Erlang C values be greater than one?

Here is an Erlang C plot I did myself. The x-axis represents the total traffic while the y-axis represents the probability. Each line represents a different total number of channels. As you can see, ...
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1answer
58 views

Why are Erlang B and Erlang C formulas different?

Erlang B determines the probability that a call is blocked and is defined as: $$Pr[blocking]= {{A^C \over C!} \over {\sum_{k = 0}^{C} {A^k \over k!}}}$$ while Erlang C determines the probability ...
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10answers
12k views

Can a premium HDMI cable outperform a standard cable?

Assuming two cables both conform to the same standards (e.g. HDMI2.0, high-speed, ...) is it possible that a premium cable will outperform a standard cable when using an objective benchmark that ...
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1answer
17 views

dsb_sc of sin wave

Can we take the dsb_sc(Double side band suppressed carrier)of a sinusoidal signal I know that it exists for cosine but for sine I can't find anything on the internet
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1answer
104 views

Transmitter and Receiver antennas in mobile phones

I understand that in old cellular systems where FDD were employed, we used to have same antenna at the mobile phone (User equipment) for transmission and reception.Moreover, a duplexer was used to ...
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1answer
420 views

Analog beamforming vs digital beamforming

I am reading some research articles on wireless communication where they talk about beamforming techniques and their differences in Multiple antenna Tx-Rx systems (MIMO). It says analog beamforming ...
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2answers
44 views

Pulse Train Sampling Rate

Assume I have a pulse train with frequency of F Hertz. A normal square wave has all odd harmonics. From Nyquist, if I want to "Reconstruct" the waveform, sampling frequency Fs should be at least 2*(...
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7answers
5k views

Is it possible to send multiple data bits on a single wire at once?

Is there an existing protocol or modulation method where multiple data bits are sent over a single wire at once or maybe an additional ground line (like serial communication)? I know there are ...
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0answers
52 views

How do I get the FSM table from the given diagram?

Given one is question and another solution. I cant come to this solution. can anyone help here
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1answer
86 views

How do I get the sum and carry expression for ripple carry adder?

please check the photo and kindly let me know how to find the expression. I know sum expression only with xor gate. Cannot come to this conclusion.
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1answer
42 views

Identification of line code from amplitude, phase and PSD plots

I recorded some transmitted data using the Noo-Elec RTL2832 software-defined radio. The data is transmitted at a carrier frequency of 1.3GHz and sampled at 2.4MHz. The transmitted data is a set of ...
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8answers
8k views

Why is digital serial transmission used everywhere? i.e. SATA, PCIe, USB

While looking at SATA, PCIe, USB, SD UHS-II it struck me that they are all the same: digital serial bitstream, transmitted using differential pairs (usually 8b/10b coded), with some differences in ...
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1answer
83 views

How to use multiplexor 74HC4067

I am using 74hc4067 IC(Multiplexer 4:16) for the extend the gpio pins can i use that gpio pins same time or not? and any one suggest about the ic how it is used?
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1answer
35 views

Method to find Correlation for a random variable and thereby power spectral density of random signal

I'm trying really hard to understand the segment of text from a standard communication book ( Modern digital and analog communications by B P Lathi). We are trying to find the power spectral density ...
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0answers
14 views

Is there a stated tolerance on IRIG-B pulse lengths?

I've been looking at IRIG-B lately, and while I see that the expected pulse lengths are 2 ms, 5 ms, and 8 ms, I haven't seen specification of how much these pulse lengths are allowed to differ from ...
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1answer
54 views

How to determine data transmission rate from an eye diagram?

I would like to know how to determine the data transmission rate from an eye diagram such as the one given below: Would it be the reciprocal of the length of time from the start of the diagram to ...
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1answer
102 views

Arduino Fails to Program Custom NRF52, But Has Worked In Past

Background: I have a custom board that consists of two PCBs connected via a 100mm Picoblade connector. The "Aux" board has a USB port, and CP2102N Serial=>USB converter. The "Main" board has an NRF52 ...
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0answers
86 views

Fast driving long cable

I'm trying to send digital data over 50 meter wire (0V, 36V) using 5V logic (atmega). Signal frequency will be around 8kHz, would be nice if it would work with frequency up to 16kHz. Whole connection ...
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4answers
153 views

Phase Shift Keying: Is it ever actually used?

during my course in digital communications Phase Shift Keying is talked about where the modulation consisted of altering the phase of the carrier signal. This process takes up a lot of spectrum so I ...
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0answers
42 views

Ladder Logic BCD Communications

I have a very limited number of outputs available (4 to be exact) on my existing PLC and need to share 5-7 bits of information to another PLC without having the expense off add-on communication cards. ...
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1answer
23 views

Calculating throughput of BPSK channel with roll-off, error correction code, packet loss

A digital signal is transmitted with packets of: 240 bytes of information. control header of 10 bytes. reference signal of 700 μs/packet BPSK modulation. rolling factor of 0.25 1 MHz band. coding ...
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2answers
90 views

Uploading program to a MCU

I'd like to start my own personal project on making a small device using MCU. I am currently researching the things that I need to know and buy. I think I am going to use MCU bluenrg by STM. I was ...
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1answer
28 views

source and channel encoding. can they be done together?

Why are source and channel encodings usually performed separately? Could they be made together? thanks!
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0answers
48 views

Why do we need an (adaptive) equalizer when we have a matched filter at the receiver?

When both can perform the same task of reducing the effects of ISI, why use both and not just one at the receiver end?
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3answers
91 views

Unsure how arduino is interpreting RS232 signal

Disclaimer: I am a novice. I have an RS232 connection with an RFID tag reader which I am monitoring via software on a desktop computer as well as an Arduino. The device is configured with 8E1 parity. ...
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1answer
43 views

Tail biting Convolution Encoder

I understand how encoder and decoder works but what are theses values ??